(1) Field of the Invention
The present invention relates to an electronic component comprising a metallic case or casing, in particular, to an electronic component comprising a metallic case provided with a magnetic loss material, which uses a magnetic substance having a great magnetic loss characteristic at a high frequency and in which the magnetic substance has an excellent complex permeability characteristic effective in suppression of electromagnetic interference and undesired radiation caused by reflection or resonance of a metallic case questioned in a high-speed operation type of active element or a high frequency electronic component and an electronic apparatus.
(2) Description of the Related Art
Recently, a high-speed operation type of highly integrated semiconductor device has been spread significantly. As an example, a logic circuit element such as a random access memory (RAM), a read only memory (ROM), a microprocessor (MPU), a central processing unit (CPU), or an image processor arithmetic logic unit (IPALU) is known. In relation to these active elements, calculation speed and signal processing speed are rapidly made higher, so that an electric signal transmitting through a high-speed electronic circuit is a main cause of a dielectric high frequency noise since it is accompanied with a rapid change in electric voltage and current.
On the other hand, lightening, thinning, and miniaturizing of an electronic component and apparatus make unlimitedly rapid progress. Accordingly, the integration degree of a semiconductor device and the packaging density of an electronic component on a printed wired board are significantly made higher. Thus, tightly integrated or packaged electronic elements or signal lines are disposed extremely close to each other. This and the aforementioned high-speed signal processing would easily cause the electromagnetic interference, which affects even a high frequency, or a radiation noise.
In such a recent electronic integrated element or wired board, a problem is pointed out in relation to the undesired radiation from a current supplying line to an active element. As a countermeasure against the problem, a concentrated constant component, such as a decoupling condenser, is inserted in the current supplying line, for example.
In the high-speed electronic integrated element or wired board, however, it has occurred that the noise-countermeasure, which uses a conventional concentrated constant circuit as a prerequisite, has no effect since the signal path operates as a distributed constant due to the generated noise including a higher harmonic component.
Further, an electronic component comprising a metallic case or casing, which will be hereinafter referred to as a metallic case, has a problem that the electromagnetic interference or undesired radiation is caused by radiation or resonance of the metallic case.
It is an object of the invention to provide an electronic component comprising a metallic case in which the electromagnetic interference and undesired radiation, which are caused by the metallic case accommodating such high-seed operation type of semiconductor device and electronic circuit, are reduced.
According to the present invention, there is provided an electronic component comprising an electronic circuit or a circuit element in a metallic case. In the present invention, the metallic case is provided with a magnetic thin film made of a magnetic loss material.
Here, in the electronic component comprising a metallic case according to the invention, it is preferred that the magnetic thin film is provided in a place of the metallic case where the high frequency current passes or on at least part of an inner wall surface of the metallic case.
On the other hand, in the electronic component comprising a metallic case according to the invention, it is preferred that the magnetic thin film is made of a magnetic loss material. The magnetic loss material has a composition represented by M-Xxe2x80x94Y, wherein M denotes at least one of Fe, Co and Ni, X denotes at least one of elements other than M and Y, and Y denotes at least one of F, N and O. The magnetic loss material is a narrow band magnetic loss material such that the maximum value xcexcxe2x80x3max of an imaginary part xcexcxe2x80x3 exists in a frequency range of 100 MHz to 10 GHz in complex permeability characteristics and that a relative bandwidth bwr is not greater than 200% where the relative bandwidth bwr is obtained by extracting a frequency bandwidth between two frequencies at which the value of xcexcxe2x80x3 is 50% of the maximum xcexcxe2x80x3max and normalizing the frequency bandwidth at the center frequency thereof. Otherwise, it is preferred that the magnetic thin film is made of a magnetic loss material having a composition represented by M-Xxe2x80x94Y, wherein M denotes at least one of Fe, Co and Ni, X denotes at least one of elements other than M and Y, and Y denotes at least one of F, N and O. The magnetic loss material is a broad band magnetic loss material such that the maximum value xcexcxe2x80x3max of an imaginary part xcexcxe2x80x3 exists in a frequency range of 100 MHz to 10 GHz in complex permeability characteristics and that a relative bandwidth bwr is not smaller than 150% where the relative bandwidth bwr is obtained by extracting a frequency bandwidth between two frequencies at which the value of xcexcxe2x80x3 is 50% of the maximum xcexcxe2x80x3max and normalizing the frequency bandwidth at the center frequency thereof.